Revert of Remove VCMQmRobustness. (patchset #1 id:1 of https://codereview.webrtc.org/1917083003/ )

Reason for revert:
Speculative revert for perf regression.

Original issue's description:
> Remove VCMQmRobustness.
>
> Class contained a lot of not-really-wired-up functionality that ended up
> being complicated ways of saying return 1; or return false;. This
> removes this dependency that complicates code readability significantly.
>
> BUG=webrtc:5066
> R=marpan@google.com, marpan@webrtc.org
> TBR=stefan@webrtc.org
>
> Committed: https://crrev.com/73894369791cb5eedc8788baf918ec07d11d351d
> Cr-Commit-Position: refs/heads/master@{#12516}

TBR=marpan@webrtc.org,stefan@webrtc.org,marpan@google.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5066, chromium:607838

Review-Url: https://codereview.webrtc.org/1935753002
Cr-Commit-Position: refs/heads/master@{#12572}

webrtc/modules/video_coding/qm_select.h

@@ -322,5 +322,35 @@ class VCMQmResolution : public VCMQmMethod {
   int num_layers_;
 };
 
+// Robustness settings class.
+
+class VCMQmRobustness : public VCMQmMethod {
+ public:
+  VCMQmRobustness();
+  ~VCMQmRobustness();
+
+  virtual void Reset();
+
+  // Adjust FEC rate based on content: every ~1 sec from SetTargetRates.
+  // Returns an adjustment factor.
+  float AdjustFecFactor(uint8_t code_rate_delta,
+                        float total_rate,
+                        float framerate,
+                        int64_t rtt_time,
+                        uint8_t packet_loss);
+
+  // Set the UEP protection on/off.
+  bool SetUepProtection(uint8_t code_rate_delta,
+                        float total_rate,
+                        uint8_t packet_loss,
+                        bool frame_type);
+
+ private:
+  // Previous state of network parameters.
+  float prev_total_rate_;
+  int64_t prev_rtt_time_;
+  uint8_t prev_packet_loss_;
+  uint8_t prev_code_rate_delta_;
+};
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_VIDEO_CODING_QM_SELECT_H_